Please note that what you’re seeing is not an error, but rather a warning. It typically occurs when you import a different bot. For instance, if you create a bot and upload 10 documents, those documents will be stored in the documents’ database. However, if you then upload a different bot, those documents no longer exist in the new bot, yet they remain in the documents’ database, and your published bot will continue to answer questions using those documents.  Clicking the button essentially means “Please go ahead and synchronize my documents.” This warning is just to alert you before deleting any documents. If you choose to remove the documents, it will affect the bot’s responses, even if the bot has not been published. If you no longer need the documents, feel free to delete them.